An army officer accused of falsifying records for Afghan prisoners has taken the stand at a court martial in Canberra.

Major David Sperry Pratt is accused of failing to record a request from an Afghan prisoner to make a complaint about mistreatment.

The allegation was raised by corporal Aaron Sweet who was also serving in Afghanistan.

He had also interviewed the prisoner who had a black eye and blood on his face.

Corporal Sweet previously told the court martial, Major Pratt recorded in an official prisoner capture log book that the man had said 'you have been good to me, I am happy' but did not mention any complaint of mistreatment.

Major Pratt told the hearing he did not believe Corporal Sweet was in the room when he spoke to the man.

He says the prisoner told him he was hit when he was caught but he did not want to complain.

Major Pratt has emphatically denied recording a request to complain or telling corporal Sweet that less is best for paperwork.

But major Pratt has admitted to adding details for a different prisoner under the name of another soldier who had left the facility.

He told the hearing he only intended to tidy up paperwork and did not intend to deceive anyone.